Well assuming you have a few plug-ins? Alf? reverser? Other wise you can't use Calibre for DRM'd books

. Making these instructions useless
1. Drag the .ACSM file into ADE (Adobe Digital Editions, as it's know on this site) This will unpack the file (ACSM includes .annot .png .epub files)
2. Start Calibre. Go to Add books. Search for the E-pub version of your book.
All set!